Crate good_memory_allocator
source ·Expand description
This is a linked list allocator, inspired by the dlmalloc algorithm, to be
used in no_std environments such as operating system kernels. The overhead
for each allocation is a single usize. The implementation prioritizes
runtime efficiency over memory efficiency, but also provides very good
memory utilization. The allocator is heavily tested with test cases covering
almost all code paths; fuzzing is used to cover the rest.
Usage
Create a static allocator:
use good_memory_allocator::SpinLockedAllocator;
#[global_allocator]
static ALLOCATOR: SpinLockedAllocator = SpinLockedAllocator::empty();Before using this allocator, you need to initialize it:
pub fn init_heap() {
unsafe {
ALLOCATOR.init(heap_start, heap_size);
}
}SMALLBINS_AMOUNT and ALIGNMENT_SUB_BINS_AMOUNT.
The allocator allows configuring the amount of smallbins and alignment
sub-bins that it uses. For those of you not familiar with smallbins, they
are data structures used by the allocator to keep track of free chunks. Each
smallbin is made up of multiple alignment sub-bins. The default amounts of
smallbins and alignment sub-bins used by the allocator are stored in their
respective constant DEFAULT_SMALLBINS_AMOUNT and
DEFAULT_ALIGNMENT_SUB_BINS_AMOUNT.
Increasing the amount of smallbins will improve runtime performance and
memory utilization, especially when you are making a lot of relatively small
allocation, but it will also increase the size of the Allocator struct.
Increasing the amount of alignment sub-bins will will also improve runtime
performance and memory utilization, especially when you are making a lot of
allocations with relatively large alignments, but it will also increase the
size of the Allocator struct.
It is recommended to choose a value that is a power of 2 for the alignemnt
sub-bins amount, since that will improve the memory utilization of the
smallbins’ memory.
The amount of alignment sub bins must be at least 2, otherwise you will get
a compilation error.
If you are in a memory constrained environment, you might want to use lower
values for these constants, since the size of the Allocator struct using
the default values is relatively large.
Features
spin(default): Provide aSpinLockedAllocatortype that implements theGlobalAlloctrait by using a spinlock.allocator: Provides an implementation of the unstableAllocatortrait for theSpinLockedAllocatortype.